In this video, we show you how to change the Chain Sprocket on a Stihl MS170.

Health & Safety Warning - Please ensure that you have safely prepared the machine and workspace. If you are unsure about any aspect of the task please seek professional advice.

Transcript

Today, we're going to change the Chain Sprocket on a Stihl MS170 Chainsaw. Make sure the chain is free before starting. Use a 19mm Hex Socket Spanner to loosen the two nuts that hold on the sprocket cover on the side of the machine. Then use a screwdriver to loosen the chain tensioning screw between the guide bar and the machine, you will notice the chain will begin to become slack. Continue to unscrew the two sprocket cover nuts on the side of the machine. This will allow you to remove the casing, completely freeing the chain and bar. Using a pair of pliers remove the circlip inside the chain sprocket. You can then remove the sprocket washer and chain sprocket. You may also want to remove the sprocket bearing so it doesn't get lost. Whilst the machine is stripped down you may want to check the clutch springs for wear. Place the sprocket bearing over the clutch, and fix your new chain sprocket on top. Relocate the sprocket washer on top of the new chain sprocket. Then use a pair of pliers to squeeze the circlip back into place. When placing the chain onto the guide bar make sure that the cutting edge, highlighted in red, is facing away from the body of the machine on the top edge of the guide bar. This means that the cutting edge should be facing in the direction of the blades rotation. If the chain is placed in the wrong direction it could lead to further problems, and will give the affect of a blunt chain. This should be avoided by taking the correct precautions. Place the chain around the bar. Pick the bar up and feed the chain round by pulling it around the bar. Make sure the chain moves in a smooth motion and doesn't snag. Place the chain around the chain sprocket. Make sure the two screws are seated in the opening in the guide bar. Place the casing back on and hand screw on the two nuts. Using the screwdriver to tighten the chain tensioning screw between the guide bar and the machine. Once together, make sure the chain is moving smoothly and isn't too tight and doesn't have excessive slack. That's how you change the Chain Sprocket on the Stihl MS170. All the parts & tools needed for this task are listed in the description below.

Parts

Parts and tools included in the MS170 how-to video.

• Sprocket Cover Nut M8 - 0000 955 0801
• Chain Sprocket 3/8" Picco 6T - 1123 640 2003
• Chain Sprocket 3/8" Picco 6T - 350 088
• Chain Sprocket Cover (Quick Tensioner) - 1123 640 1700
• Sprocket Bearing 10x13x10mm - 9512 933 2260
• Sprocket Washer 27mm - 0000 958 1022
• 13/19mm Combination Plug/Bolt Spanner - 902 1361
• N/G Torx Wrench/Plug Spanner (13mm & 19mm) - 410 250